I have some small amount of other patches after this, but more "TBD", which is to make the client fail hard when setting a lower API version, even when done manually (WithVersion, WithVersionFromEnv)

Some tests to look into w.r.t. MacAddress (either test is wrong, or something broke).

We also need to

• check for integration tests that are overriding API versions (may be easier to find those if we disallow setting old API versions I guess)
• but if we don't allow old versions; we wouldn't be able to test the daemon downgrading to old versions, so either raise the daemon limit as well,
  or (which we should do either way); document old API versions as "degraded" / "partial support", and better outline what our intent is for old
  API versions.

=== RUN   TestMacAddressIsAppliedToMainNetworkWithShortID
    run_linux_test.go:291: assertion failed: 1a:4c:73:5a:5f:40 (c.NetworkSettings.Networks["testnet"].MacAddress string) != 02:42:08:26:a9:55 (string)
--- FAIL: TestMacAddressIsAppliedToMainNetworkWithShortID (3.82s)

=== RUN   TestInspectCfgdMAC/ctr-wide_address_default_bridge
    mac_addr_test.go:230: assertion failed: 
        --- configMAC
        +++ tc.desiredMAC
          string(
        - 	"",
        + 	"02:42:ac:11:00:42",
          )
        

=== RUN   TestWatchtowerCreate
    mac_addr_test.go:281: assertion failed: 16:91:31:ac:a5:81 (netSettings.MacAddress string) != 02:42:ac:11:00:42 (ctrMAC string)

OK; let's bring this one in 👍